PA system rebuild project

[jont]

Re: PA system rebuild project

IMO, no, it isn't. The LAB is a great driver when used as intended, in a horn. In a reflex box it has poor sensitivity. I use it in horns, I'd never use it in direct radiators.

Have you checked out Welters design?
I was skeptical of the driver choice but it pulls good numbers below 40hz compared to traditional 18 subs.

There is a comparison at the link posted above with a SRX728, EV QRX, and EAW SB1000.


"These popular dual 18''s all have a large upper sensitivity advantage compared to the Lab 2x12''.

All the cabinets still adhere to Hoffman's Iron Law, their sensitivity in the 30 to 40 Hz range is very similar.

Below 40 the difference between the dual 18s and the 2x12'' is only about 3 dB, so a pair of the 2x12'', which take up less space than a single dual 18, would have about equal sensitivity down low.

However, the 728 can not take close to full power down low without exceeding Xmax, while the Lab 12s can. Four Lab 12 can take the same power as two of the JBL 18'', and will have less distortion down low.

From previous listening experience, I'd reckon the JBL to be cleaner than the other two dual 18s when pushed hard.

The Lab 12 design, having very flat response, does not require out of band EQ, so it ''plays well'' with with any top cabinets that have flat response at the crossover point.

Makes getting things to sound ''real'' a lot easier, especially if setting crossover points ''by ear'', or using crossovers that don't have delay, EQ, or the ability to have different crossover frequencies between low and mid.

Art Welter"

[DrummerLikesSpeakers]

Re: PA system rebuild project

Define "small". What are the ideal subwoofer cabinet dimensions for your stated requirement? What output level would you be comfortable with?

For example, in general terms, a 10"er would be in a cab as small as 12"-13" cubed or as big as 14"-15" cubed. I wouldn't want to go much bigger unless absolutely necessary. Some of the Faital Pro 10s have enough sensitivity and high power to produce better than 120 db, which I would like. The drivers don't have to be "sub" (fs below 50hz) -- there's some good mid-bass speakers that have good sensitivity down close to 50hz. If ducting can extend the bottom (with some beneficial damping) and keep the size down, great, though a sealed box would be good for clarity and punch (not sure how big a sealed box would have to be, but I assume bigger than a ducted box).

[billfitzmaurice]

Re: PA system rebuild project

Below 40 the difference between the dual 18s and the 2x12'' is only about 3 dB

Below 40Hz who cares? For live sound there's no need for anything below 40Hz, and for most genres of recorded sound there's not much happening there either.
As a direct radiator the LAB 12 works no better for pro sound than any of a dozen or more home theater twelves, because that's what it is spec wise. It even shares most of its components with a number of Eminence OEM home theater twelves. What sets it apart is the oversized dust cap that strengthens the cone for use in a horn at full excursion without the potential for cone shredding. If you're not horn loading it you might as well use an Ultimax 12.

[DrummerLikesSpeakers]

Re: PA system rebuild project

I am now looking more closely at going with Vifa ox20sc00-04 3/4" dome tweeters (no faceplate) for the high end http://www.parts-express.com/pe/show...umber=264-1002 after reading more about CBT theory/papers. One comparison paper showed very well the advantages of the arc array. The closest I have found to what I would want to buy is the TOA HX-5 "variable dispersion" line array system. I have talked to an engineer/musician with experience using them subed for portable live music apps.
The plan would be to build a verticle line array system, with each speaker cab containing a 130w AES 6.5" woofer (or maybe two) and 5 of the 20w rms 3/4" dome tweeters (1.3").The dimensions are a good match.
Those tweeters have a 1060 hz fs -- I have looked at the response curve which drops off about 3 db from there down to 1.0k. I would like to cross over no higher than 1.0k to maintain near-field coupling for the woofers (about a 1025 hz limit, or am I too concerned about that?). If I did that with a 24 db/oct slope could I satisfactorily avoid distortion? I haven't seen any distortion curves for this tweeter, and I have emailed the company about this.

Also, I have no experience with mounting a tweeter with no faceplate. Any suggestions would be appreciated. One idea I came up with is to have something mounted in a mounting board verticle slot to plug the tweeter terminals into (not sure if the tweeter configuration would allow for that). I would want to have the tweeters removeable.

[DrummerLikesSpeakers]

Re: PA system rebuild project

Since my last post I have made a move or two on my sound system project (it's about time!).
I decided to go with the all-cone line source idea for mids/highs and purchased a couple of Carvin TRX 3903 columns w/9x3" Faital Pro drivers per module http://www.carvinguitars.com/products/TRX3903, with expectations of adding a couple more. Sensitivity is 100db while output is about 122db continuous/rated 128db peak/module. I like the 21 lbs/module. They can crossover as low as [email protected]/oct or [email protected]/oct. They roll off sharply below 200hz so I'll probably cross them no lower than [email protected]/oct, but more like 250hz and as high as 400hz.

Today I talked to a Parts-Express techy about subs to get a better fix on how to achieve my objectives. To replace my old 2x15 Martin horns I want smallish, lightweight single subs and will go with neo drivers despite their higher cost -- weight is important to me. I could put the old Altec 421As from the Martins in single cabs but they are appreciably heavier than I want @ approx. 20 lbs each. And although they sound great, with good sensitivity @ 100db, they can only handle 100w RMS (maybe 150)continuous.
I emailed the techy these drivers for modeling (all Faital Pro):
12FH520 -- 12" http://www.parts-express.com/pedocs/...ifications.pdf
15HP1020 -- 15" http://www.parts-express.com/pedocs/...ifications.pdf
18HP1020 -- 18" http://www.parts-express.com/pedocs/...ifications.pdf
18FH500 -- 18" http://www.parts-express.com/pedocs/...ifications.pdf

These are all high power woofers with good sensitivity/high output.

One of my desires is for subs with a small footprint (lower Qts drivers?) and tight bass sound, and so I'm willing to go as small as 12" drivers, although I'll need more of them for output to match the columns. For example, using the 12FH520 would require 2 subs per mid-high module for a good match @ crossover. The techy also said, however, that concerns about the transient response of 18"s are not worth worrying about even if I want to cross over as high as 500hz, but that the kind of bass sound would be more a matter of taste. What 18" subwoofer characteristics would produce a "tight" sounding low end (50-150hz)? A low Qts driver/smaller cab? If an 18" sub can produce the tightness of a 12", I'll gladly go with that and the added efficiency.

Also, I have the WinISD program as a free basic speaker designer but would like to find something more versatile and also give cutout diagrams. Any suggestions?

Thanks for any helpful hints.

[kblackmore]

Re: PA system rebuild project

If you liked your previous system and just wanted something more powerful, you might consider some coax speakers. The B&C 8CX21 8" speakers have 100° x 100° coverage and should do very well when stacked. Your Martin's should do very well for the bass, just don't expect them to go as low as subs. I built a similar system for a friend who wanted a "line array" system a few years ago, those cabinets (4 stacked each side) had 3 drivers each, with the coax sitting between 2 12" woofers and used a 2 X 18" sub on each side for the bottom. The system was very loud, clear, and had great coverage (coverage was more like point source than line array). Shouldn't need much processing as we just used a crossover, separate amps and equalizer.

[Paul O]

Re: PA system rebuild project

The techy also said, however, that concerns about the transient response of 18"s are not worth worrying about

Exactly, you have likely been using those old Martin W bins without any processing whatsoever which means the transient response was a lot worse than any reflex 18 sub could ever be.

Also, I have the WinISD program as a free basic speaker designer but would like to find something more versatile and also give cutout diagrams. Any suggestions?

Be sure to use the Pro version so that you can model excursion, port velocity, and actual power handling.

[DrummerLikesSpeakers]

Re: PA system rebuild project

Your Martin's should do very well for the bass, just don't expect them to go as low as subs.

Right. The Martins are great for punch (60-80hz), but not meant for the lower regions.

[DrummerLikesSpeakers]

Re: PA system rebuild project

I built a similar system for a friend who wanted a "line array" system a few years ago, those cabinets (4 stacked each side) had 3 drivers each, with the coax sitting between 2 12" woofers and used a 2 X 18" sub on each side for the bottom. The system was very loud, clear, and had great coverage (coverage was more like point source than line array).

Sounds similar to some manufactured systems I've seen, like the PreSonus StudioLive 328 AI.

[DrummerLikesSpeakers]

Re: PA system rebuild project

Be sure to use the Pro version so that you can model excursion, port velocity, and actual power handling.

I had problems with the Pro version. First I tried an install into Win 7 which didn't work because it was meant for earlier OSs. I installed it into my XP but the "box shape" didn't work -- a message said something like "the box shaper wasn't provided with this alpha version". I've been using the "regular" (consumer) version which isn't bad -- don't know about excursion or actual power handling, but it shows port velocity.

[DrummerLikesSpeakers]

Re: PA system rebuild project

I have now settled on a choice between three neo 18" woofers for subwoofer cabs:

Faital Pro 18HP1040: Qts=0.34; Vas=208.7 L; BL=24.50; SPL=99.0; Fs=38.0; Xmax=9.5mm

Faital Pro 18HP1020 (recommended version for horns): Qts=0.28; Vas=219.0 L; BL=27.20; SPL=99.0; Fs=35.0; Xmax=9.5mm

Radian 2218 Neo: Qts=0.22; Vas=355.8 L; BL=33.06; SPL=100.0; Fs=28.97; Xmax=21+mm (yes, 21!). The Radian incorporates 2 stacked neo magnetes w/extra long gap.

The Radian is the beast! The Faital Pros accept 1000 watts cont., and the Radian 1300 watts cont..
Each have their advantages.

I want to high pass @ 40hz, 24db/oct. and will cross over w/mid-high cabs @ 200hz, 24db/oct, possibly as high as 400hz.

Bill FM has said that a high BL, especially over 30, tends to "choke-off" the lower frequencies with a faster roll-off and needs more excursion and power. High BL produces a "faster" more forceful diaphram action, and can enhance punch and tightness in the lower regions (<60hz). Stuffing can also do some of that (damping?).
That said, I want slot-vented subs that have good punch (but not extreme) and tightness, in small-medium lightweight cabs. Some guidelines I've seen suggest that Qts <.26 will be harder to design around and will end up requiring more EQing.

What is an "average" range of BL for 18"ers? I've heard maybe 18-23.

And of course there's always the power compression factor that most speaker makers seemm to be afraid of publicizing.

Any thoughts soon would be greatly appreciated.

[jont]

Re: PA system rebuild project

Radian x-max is likely not 21mm. I think that it is the point to point measurement.
JBL has a few models in the catalog that are also (creatively) measured.

Since budget is not the limiting factor you could look at the TC sounds pro 5100 18"

[DrummerLikesSpeakers]

Re: PA system rebuild project

Radian x-max is likely not 21mm. I think that it is the point to point measurement.
JBL has a few models in the catalog that are also (creatively) measured.

A Radian engineer has told me that 21mm is the Xmax, not the Xlimit. But your point about creative measurement is well-taken.

Since budget is not the limiting factor you could look at the TC sounds pro 5100 18"

I've looked at that speaker, which looks like one referred to as the "bee-hive". The BL looks to be quite low for the Qts, and the sensitivity of 94.5 db indicates average efficiency at best.

[jont]

Re: PA system rebuild project

Look at efficiency in the frequency band where you will be using it (software models) the 99db/watt is not measured @ 50-80hz with pro-sound drivers.

Generating low frequencies with a small light reflex box means you will need to move some air = xmax and power.

About the Radian, check out post #14 and #19 http://www.diyaudio.com/forums/subwo...m-x-max-2.html

[DrummerLikesSpeakers]

Re: PA system rebuild project

Look at efficiency in the frequency band where you will be using it (software models) the 99db/watt is not measured @ 50-80hz with pro-sound drivers.

After I see the "rated" sensitivity I look at the response curve to tell me the sensitivity in the regions of my interest. For a general sensitivity rating I think the Reference Efficiency in decibels is more honest. One such calculator is at: http://www.bcae1.com/spboxad2.htm

About the Radian, check out post #14 and #19 http://www.diyaudio.com/forums/subwo...m-x-max-2.html

Thanks for the link -- all I know is the Radian engineer that I have been dealing with says the advertised 18" X-max is accurate. Apparently they incorporate a double (stacked) neo magnet for extra depth and gap length (same for the 15"). I have, however, noticed an inconsistancy or two in their claims and they don't list the X-damage.